sigv4.h

#ifndef __AWS_SIGV4_H
#define __AWS_SIGV4_H

/*
  Replace the standards header files with a single system-specific header file.
  Value must include quotes, for example `#define SIGV4_SYSTEM_HEADER "foo.h"
*/
#ifdef SIGV4_SYSTEM_HEADER
#include SIGV4_SYSTEM_HEADER
#else
#include <stdarg.h>
#include <stddef.h>
#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include <ctype.h>
#endif

#define AWS_SIGV4_BUFFER_OVERFLOW_ERROR -2
#define AWS_SIGV4_INVALID_INPUT_ERROR -1
#define AWS_SIGV4_OK 0
#define AWS_SIGV4_MAX_NUM_HEADERS 10
#define AWS_SIGV4_AUTH_HEADER_MAX_LEN 2048

typedef struct aws_sigv4_str_s
{
  unsigned char *data;
  unsigned int len;
} aws_sigv4_str_t;

typedef struct aws_sigv4_kv_s
{
  aws_sigv4_str_t key;
  aws_sigv4_str_t value;
} aws_sigv4_kv_t;

aws_sigv4_str_t aws_sigv4_string(const unsigned char *cstr);

int aws_sigv4_strcmp(aws_sigv4_str_t *str1, aws_sigv4_str_t *str2);

int aws_sigv4_empty_str(aws_sigv4_str_t *str);

unsigned char *aws_sigv4_sprintf(unsigned char *buf, const char *fmt, ...);

unsigned char *aws_sigv4_snprintf(unsigned char *buf, unsigned int n, const char *fmt, ...);

typedef aws_sigv4_kv_t aws_sigv4_header_t;

typedef int (*aws_sigv4_compare_func_t)(const void *, const void *);

typedef struct aws_sigv4_params_s
{
  /* AWS credential parameters */
  aws_sigv4_str_t secret_access_key;
  aws_sigv4_str_t access_key_id;

  /* HTTP request parameters */
  aws_sigv4_str_t method;
  aws_sigv4_str_t uri;
  aws_sigv4_str_t query_str;
  aws_sigv4_str_t host;
  /* x-amz-date header value in ISO8601 format */
  aws_sigv4_str_t x_amz_date;
  aws_sigv4_str_t payload;

  /* if true, use UNSIGNED-PAYLOAD for x-amz-content-sha256 */
  bool unsigned_payload;

  /* AWS service parameters */
  aws_sigv4_str_t service;
  aws_sigv4_str_t region;

  /* Additional headers */
  aws_sigv4_kv_t headers[AWS_SIGV4_MAX_NUM_HEADERS];
  unsigned int num_headers;

  /* Sorting function */
  void (*sort)(void *base, size_t n, size_t size,
               aws_sigv4_compare_func_t cmp);

  /* SHA256 function */
  void (*sha256)(const unsigned char *data, unsigned int len, unsigned char *out);

  /* HMAC SHA256 function */
  int (*hmac_sha256)(const unsigned char *data, size_t data_len,
                     const unsigned char *key, size_t key_len,
                     unsigned char *out, size_t *out_len);

} aws_sigv4_params_t;

/** @brief get hex encoding of a given string
 *
 * @param[in] str_in    Input string
 * @param[out] hex_out  Output buffer to store hex encoded string
 */
void get_hexdigest(aws_sigv4_str_t *str_in,
                   aws_sigv4_str_t *hex_out);

/** @brief get hex encoded sha256 of a given string
 *
 * @param[in] sigv4_params      Pointer to a struct of sigv4 parameters
 * @param[in] str_in          Input string
 * @param[out] hex_sha256_out Output buffer to store hex encoded sha256 string
 */
void get_hex_sha256(aws_sigv4_params_t *sigv4_params,
                    aws_sigv4_str_t *str_in,
                    aws_sigv4_str_t *hex_sha256_out);

/** @brief derive signing key
 *
 * @param[in] sigv4_params  Pointer to a struct of sigv4 parameters
 * @param[out] signing_key  Struct of buffer to store derived signing key
 */
void get_signing_key(aws_sigv4_params_t *sigv4_params,
                     aws_sigv4_str_t *signing_key);

/** @brief get credential scope string
 *
 * @param[in] sigv4_params      Pointer to a struct of sigv4 parameters
 * @param[out] credential_scope Struct of buffer to store credential scope string
 */
void get_credential_scope(aws_sigv4_params_t *sigv4_params,
                          aws_sigv4_str_t *credential_scope);

/** @brief get signed headers string
 *
 * @param[in] sigv4_params    Pointer to a struct of sigv4 parameters
 * @param[out] signed_headers Struct of buffer to store signed headers string
 */
void get_signed_headers(aws_sigv4_params_t *sigv4_params,
                        aws_sigv4_str_t *signed_headers);

/** @brief get canonical headers string
 *
 * @param[in] sigv4_params        Pointer to a struct of sigv4 parameters
 * @param[out] canonical_headers  Struct of buffer to store canonical headers string
 */
void get_canonical_headers(aws_sigv4_params_t *sigv4_params,
                           aws_sigv4_str_t *canonical_headers);

/** @brief get canonical request string
 *
 * @param[in] sigv4_params        Pointer to a struct of sigv4 parameters
 * @param[out] canonical_request  Struct of buffer to store canonical request string
 */
int get_canonical_request(aws_sigv4_params_t *sigv4_params,
                          aws_sigv4_str_t *canonical_request);

/** @brief get string to sign
 *
 * @param[in] sigv4_params      Pointer to a struct of sigv4 parameters
 * @param[in] request_date A pointer to a struct of request date in ISO8601 format
 * @param[in] credential_scope  Pointer to a struct of precomputed credential scope
 * @param[in] canonical_request Pointer to a struct of precomputed canonical request
 * @param[out] string_to_sign   Struct of buffer to store string to sign
 */
void get_string_to_sign(aws_sigv4_params_t *sigv4_params,
                        aws_sigv4_str_t *request_date,
                        aws_sigv4_str_t *credential_scope,
                        aws_sigv4_str_t *canonical_request,
                        aws_sigv4_str_t *string_to_sign);

/** @brief perform sigv4 signing
 *
 * @param[in] sigv4_params  A pointer to a struct of sigv4 parameters
 * @param[out] auth_header  A struct to store Authorization header name and value
 * @return Status code where zero for success and non-zero for failure
 */
int aws_sigv4_sign(aws_sigv4_params_t *sigv4_params, aws_sigv4_header_t *auth_header);

#endif /* __AWS_SIGV4_H */